The objective of this investigation is to study the recognition sites of AA-tRNA on ribosomes with special emphasis on the role of the omega loop of tRNA. Toward this end the preparation of long fragments from specific tRNAs (including those from neoplastic tissues) having an aminoacyl or N-acylaminoacyl residue on the 3' end will be carried out. The introduction of the amino acid will be performed enzymatically or chemically. The binding and transfer properties of the above compounds in homologous and heterologous bacterial, mammalian and tumor ribosomal systems will be investigated, particularly with the goal of better characterizing tRNA binding sites. This investigation will attempt to establish whether or not there are differences in the binding of neoplastic and normal tRNA fragments to ribosomes from normal and neoplastic tissues. The study of translocation of long N-acyl-AA-tRNA fragments uncoupled from mRNA movement will be carried out. The aim will be to elucidate the possible relationship of the tRNA ribosomal binding sites with the translocational C site.